Starting a Stihl MS170 chainsaw for the first time, or after it’s been sitting for a while, can seem a little daunting. Can you start a Stihl MS170 without priming? Yes, you can attempt to start it without priming, but it’s not recommended and often makes it much harder. This guide will walk you through the simple steps to get your Stihl MS170 up and running smoothly, ensuring a safe and efficient experience.
Getting Your Stihl MS170 Ready: Pre-Start Essentials
Before you even think about pulling the cord, there are a few crucial steps to ensure your Stihl MS170 is prepped and ready for action. This preparation is key to a successful start and prevents potential damage.
Fueling Your Chainsaw: The Right Mix Matters
The Stihl MS170, like most modern gasoline-powered chainsaws, requires a specific fuel mix to operate correctly. Using the wrong mixture can lead to engine damage, poor performance, and premature wear.
What is the Correct MS170 Fuel Mix?
Stihl recommends using a mix of high-quality, unleaded gasoline and a specific Stihl 2-stroke engine oil. The standard ratio for the Stihl MS170 is 50:1. This means for every 50 parts of gasoline, you need 1 part of 2-stroke oil.
- Gasoline: Always use fresh, unleaded gasoline with an octane rating of 89 or higher. Avoid ethanol-heavy fuels if possible, as they can degrade fuel system components over time.
- 2-Stroke Oil: Use a premium 2-stroke engine oil specifically designed for air-cooled engines, such as Stihl’s own HP Ultra 2-stroke oil or an equivalent quality oil that meets the JASO FD or ISO-L-EGD standards.
How to Mix Fuel for Your Stihl MS170
Mixing the fuel correctly is straightforward:
- Measure your gasoline: Determine how much fuel you need. For a small amount, 1 gallon (or about 4 liters) is a good starting point.
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Calculate the oil: For a 50:1 mix, you’ll need 2.6 fluid ounces (or about 77 ml) of 2-stroke oil per gallon of gasoline.
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Conversion Table for Fuel Mixing:
Gasoline Amount (US Gallons) Gasoline Amount (Liters) Stihl 2-Stroke Oil (fl oz) Stihl 2-Stroke Oil (ml) 1 ~3.78 2.6 ~77 2 ~7.57 5.2 ~154 3 ~11.35 7.8 ~231 4 ~15.14 10.4 ~308
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Combine: Pour the gasoline into a clean, approved fuel container first. Then, add the measured amount of 2-stroke oil.
- Mix thoroughly: Close the container securely and shake it well for at least 30 seconds to ensure the oil and gasoline are fully blended. It’s a good practice to shake the container again before each refueling.
Important: Never mix oil directly into the chainsaw’s fuel tank. Always use a separate, clean fuel container.
Checking the Chain and Bar
A properly functioning chain and bar are essential for safe and effective cutting.
Chain Tension
- Too loose: The chain can come off the bar while cutting, which is extremely dangerous.
- Too tight: The chain will bind and wear out the engine and bar prematurely.
How to Check and Adjust Chain Tension:
- Ensure the engine is off and cool.
- Gently pull the chain around the bar. It should move freely but feel snug against the bar’s underside.
- Check for sag: When you pull the chain down from the bottom of the bar, there should be no more than about 1/8 inch (3 mm) of slack. The chain should still “grip” the top of the bar.
- Adjust if needed:
- Loosen the bar nuts slightly (not completely off).
- Locate the tensioning screw (usually near the bar mount on the side of the saw).
- Turn the tensioning screw clockwise to tighten the chain, or counter-clockwise to loosen it.
- Periodically check the chain as you adjust.
- Once the tension is correct, retighten the bar nuts firmly.
Chain Lubrication
The Stihl MS170 has an automatic chain lubrication system. This means it automatically feeds oil from the dedicated oil tank onto the chain and bar as you cut.
- Check the oil reservoir: Ensure the chain oil tank is filled with a good quality chain and bar oil (Stihl recommends their own brand). Do NOT use motor oil or used oil.
- Clean the oiler hole: Make sure the small hole on the underside of the bar where the oil flows onto the chain is clear of debris.
The Stihl MS170 Starting Procedure: Step-by-Step
Now that your MS170 is fueled and checked, it’s time to get it started. This procedure applies whether it’s the Stihl chainsaw first start or a subsequent one.
Step 1: Setting the Chainsaw Choke
The choke is a vital component for starting a cold engine. It enriches the fuel-air mixture, making it easier for the engine to ignite.
Stihl Chainsaw Choke Setting
The Stihl MS170 has a combination throttle lock and choke lever. This lever has three positions:
- Full Choke (Cold Start): This is the position you’ll use when starting a cold engine. The lever is pushed fully down. In this position, the throttle is locked open slightly, and the choke plate restricts airflow into the carburetor.
- Half Choke (Warm Start/Runs): This is used for starting an engine that is warm or has been recently shut off. The lever is in the middle position. The choke plate is partially opened, and the throttle is still locked.
- Run (No Choke): This is the normal operating position. The lever is pulled all the way up, and the choke plate is fully open. The throttle is unlocked.
For a cold start, ensure the combination lever is in the full choke position (pulled all the way down).
Step 2: Engaging the Chain Brake
For safety, always engage the chain brake before starting the engine.
- How to Engage: Push the orange handle forward towards the front of the chainsaw. You should feel it click into place. The chain is now held stationary.
Step 3: Priming the MS170 Engine
The MS170 engine priming is a manual step that helps draw fuel into the carburetor. This is particularly important for cold starts or when the saw has been sitting idle.
MS170 Engine Priming
- Locate the primer bulb: On the side of the chainsaw, near the carburetor, you’ll see a small, clear rubber bulb.
- Press the bulb: Press the primer bulb repeatedly (usually 5-10 times) until you see fuel move through it and back into the fuel tank. You’ll see small bubbles as the fuel circulates.
What if my MS170 doesn’t have a primer bulb? Some older or simpler models might not have a primer bulb. In such cases, the “cold start” choke position does most of the priming work. However, the MS170 typically features this helpful priming mechanism.
Step 4: Starting the Engine
With the choke set, chain brake engaged, and the primer bulb pressed, you’re ready to pull the cord.
Stihl MS170 Manual Start Procedure
- Place the chainsaw on a flat, stable surface. Ensure the chain is not touching anything.
- Grip the starter handle: Firmly grasp the starter handle (the Stihl MS170 pull cord grip).
- Pull the cord: Pull the starter cord smoothly and steadily. You are aiming to pull it out about two-thirds of the way.
- Listen for a “pop”: You want to hear the engine sputter or “pop” – this indicates it’s trying to start.
- If it pops:
- Immediately disengage the chain brake (pull the orange handle back towards you).
- Move the combination throttle lock and choke lever from the full choke position to the half choke position (middle setting).
- Pull the starter cord again, this time with a few shorter, faster pulls. The engine should now start and run.
- Once the engine is running, immediately move the combination throttle lock and choke lever to the run position (all the way up). The engine may idle slightly rough at first, but it should smooth out.
- If it does NOT pop:
- Continue pulling the starter cord a few more times with the choke in the full position.
- If it still doesn’t pop, check your fuel mixture, ensure the choke is fully engaged, and try again.
Crucial Note for Starting: Always pull the cord with a firm, consistent motion. Yanking too hard or too fast can be ineffective and potentially cause strain.
Step 5: Engaging the Throttle and Letting it Warm Up
Once the engine is running and the choke is in the “run” position, you can gently squeeze the throttle trigger.
- Gentle Throttle: Allow the engine to run at a slightly elevated idle for a minute or two. This helps the engine warm up and reach its optimal operating temperature, ensuring smoother performance. You might notice a slight increase in chain speed; this is normal.
Troubleshooting Common Starting Issues
Even with the best instructions, sometimes a chainsaw can be stubborn. Here’s some common Stihl chainsaw troubleshooting for the MS170.
Stihl Chainsaw Troubleshooting: What to Do If It Won’t Start
| Problem | Possible Cause | Solution |
|---|---|---|
| Engine doesn’t sputter at all. | No fuel, incorrect fuel mix, or spark plug issue. | Check fuel level and ensure it’s fresh. Verify the fuel mix ratio. Inspect the spark plug (clean, gap, damage). |
| Engine sputters but doesn’t start. | Choke not correctly set, or needs more fuel. | Try starting with the choke in the full position again, pulling a few more times. Ensure the primer bulb was used. If it sputtered, try with the choke in the half position. |
| Engine starts then immediately dies. | Choke needs to be moved to run, or is still too rich. | Move the choke to the run position as soon as the engine sputters. If it still dies, it might be flooding; let it sit for a few minutes and try again without the choke. |
| Starter rope is hard to pull. | Engine is seized or has a mechanical issue. | Do not force it. This could indicate serious internal damage. Contact a service center. |
| Engine runs rough or stalls when throttled. | Incorrect fuel mix, dirty carburetor, or ignition issue. | Double-check the fuel mix. Consider cleaning or replacing the air filter. Inspect the spark plug. If problems persist, a carburetor adjustment or cleaning might be needed. |
Checking the Spark Plug
A faulty spark plug is a common reason for a chainsaw not starting or running poorly.
- Locate the spark plug: It’s usually under a black plastic cap on the top of the engine.
- Remove the cap: Twist and pull the cap off the spark plug.
- Remove the spark plug: Use a spark plug wrench (often included with the saw or available at hardware stores) to unscrew the spark plug.
- Inspect:
- Condition: Look for oil fouling, carbon buildup, or damage to the electrode.
- Gap: Ensure the gap between the electrodes is correct (check your MS170 manual for the exact specification, typically around 0.020 inches or 0.5 mm). You can use a feeler gauge to check and adjust if necessary.
- Clean or Replace: If the plug is fouled, you can try cleaning it gently with a wire brush and some carburetor cleaner. However, it’s often best to replace it with a new, correctly gapped plug. Stihl recommends NGK CMR6H spark plugs for the MS170.
Cleaning the Air Filter
A clogged air filter restricts airflow to the engine, making it run rich and perform poorly.
- Access the filter: Remove the top cover of the chainsaw (usually held by a knob or clip).
- Remove the filter: Carefully take out the air filter.
- Clean or replace:
- For basic cleaning: Tap the filter gently to dislodge loose debris. You can also use compressed air to blow out dust from the inside.
- For heavily soiled filters: Wash it in warm, soapy water, rinse thoroughly, and let it air dry completely before reinstalling.
- Replacement: If the filter is damaged or extremely dirty, it’s best to replace it with a new one.
Advanced Tips and Stihl MS170 Beginner Guide
For those new to chainsaws, here are some additional tips to make your experience with the Stihl MS170 smoother and safer.
Stihl MS170 Beginner Guide: Key Takeaways
- Read Your Manual: Always refer to the official Stihl MS170 owner’s manual for specific details and safety instructions.
- Safety First: Always wear appropriate Personal Protective Equipment (PPE), including safety glasses, hearing protection, gloves, and sturdy footwear.
- Proper Handling: Keep the saw firmly gripped with both hands. Never operate it one-handed.
- Cutting Technique: Let the saw do the work. Don’t force it. Use the “kickback zone” (the tip of the bar) with extreme caution, as this is where kickback is most likely to occur.
- Maintenance: Regular cleaning of the air filter, checking chain tension, and ensuring the fuel mix is correct will extend the life of your chainsaw and keep it running smoothly.
How to Start a Cold Chainsaw: A Quick Recap
The process for how to start a cold chainsaw like the Stihl MS170 is consistently:
- Fuel: Correctly mixed fuel in the tank.
- Choke: Set the combination lever to the full choke position.
- Chain Brake: Engage the chain brake.
- Prime: Press the primer bulb several times until fuel is visible.
- Pull: Pull the starter cord smoothly until the engine pops.
- Adjust Choke: Move the lever to half choke and pull again until it starts.
- Run: Move the lever to the run position.
- Warm-up: Allow the engine to idle for a short period.
What to Do After Starting
Once your Stihl MS170 is running, it’s ready for use. Remember to:
- Disengage the chain brake before you begin cutting.
- Keep the chain sharp. A dull chain makes cutting harder and can be dangerous.
- Monitor fuel levels and refuel safely when needed.
- Listen to your saw. Any unusual noises or changes in performance can indicate a problem that needs attention.
Frequently Asked Questions (FAQ)
Q1: Can I use regular gasoline without 2-stroke oil in my Stihl MS170?
A: No, absolutely not. The Stihl MS170 is a 2-stroke engine and requires a specific mix of gasoline and 2-stroke oil. Running it on straight gasoline will cause severe engine damage.
Q2: My Stihl MS170 is hard to start. What could be wrong?
A: Common reasons include incorrect fuel mix, a dirty air filter, a fouled spark plug, or the choke not being set correctly. Refer to the troubleshooting section in this guide for specific steps to diagnose and fix these issues.
Q3: How often should I check the chain tension on my Stihl MS170?
A: It’s recommended to check the chain tension frequently, especially during your first few cuts with a new chain or after extended use. A good rule of thumb is to check it every time you refuel.
Q4: What is the role of the primer bulb on the MS170?
A: The primer bulb, or MS170 engine priming system, manually pumps fuel from the fuel tank into the carburetor. This helps to get fuel into the engine, making it easier to start, especially when the engine is cold.
Q5: Is it normal for the Stihl MS170 to idle a bit rough after starting?
A: Yes, it’s normal for the engine to idle a bit unevenly for a few moments after starting, especially if it’s still a bit cool. As the engine warms up and you move the choke to the “run” position, the idle should become smoother.
By following these detailed steps and tips, you’ll be well-equipped to start your Stihl MS170 correctly and maintain it for reliable performance. Always prioritize safety and consult your owner’s manual for any specific concerns.